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2 Technical conditions The standard specifies that the product should achieve the performance indicators and quality requirements known as technical conditions, such as chemical composition, dimensions, surface quality, physical properties, mechanical properties, process performance, internal organization, delivery status, etc.
3 Guarantee conditions According to the technical conditions of metal materials, the manufacturer shall carry out inspections and ensure that the inspection results comply with the specified requirements of the performance, chemical composition, internal organization and other quality indicators, known as the guarantee conditions
(1) Basic guarantee conditions - also called guaranteed conditions, refer to those specified in the standard. Regardless of whether or not the demand side requests the order, the manufacturer must carry out the inspection and ensure that the inspection result meets the specified requirements.
(2) Additional guarantee conditions - which are stipulated in the standard. As long as the demand side specifies the requirements in the contract, the manufacturer must carry out the inspection and ensure that the inspection results conform to the specified project.
(3) Agreement guarantee conditions - items that are not specified in the standard, and that are agreed by the supplier and the buyer and specified in the contract, are called the agreement guarantee conditions
(4) Reference conditions - Items that are not specified in the standard, or are specified, and do not require assurance. Items proposed by the acquirer and agreed upon by the supplier and the buyer through consultation shall be used for reference only and not subject to assessment.
4 Quality Certificates The production of metal materials, like the production of other industrial products, is carried out in accordance with the uniform standards and the implementation of the product delivery inspection system. Unqualified metal materials are not allowed to be delivered. For the delivery of metal materials, the manufacturer provides a quality certificate to guarantee its quality. The certificate of quality of metal materials not only describes the name, specifications, number of deliveries, weight, etc. of the materials, but also provides the quality certificate of all the inspection results of the specified guarantee items, which is the supplier's confirmation and assurance of the inspection results of the batch of products. It is also the basis for the re-inspection and use of the acquirer
5 Quality grade According to the different requirements of steel surface quality, shape and size allowable deviation, the quality of steel is divided into several grades. For example, a primary product, secondary product. Sometimes, different levels are set for a certain requirement. For example, the surface quality is divided into primary, secondary and tertiary levels, and the depth of surface decarburization layer is divided into a group and a group of two groups, all of which represent quality differences.
6 Accuracy grades Some metal materials, the standard provides for several sizes allowable deviations, and according to the size of the allowable deviation is different, divided into several levels, known as the accuracy level. The accuracy level is divided into ordinary precision, higher accuracy, and advanced accuracy according to the allowable deviation. The higher the accuracy level, the smaller the allowable dimensional deviation. When ordering, care should be taken to write the accuracy level requirements into related documents such as contracts.
7 Brands The name of the metal material is the name given to each specific metal material. The steel grade is also called the steel number. The grades of China's metal materials generally reflect the chemical composition. The grade not only indicates the specific type of metal material, but also can roughly determine its quality based on it. In this way, the grades simply provide a common concept of the quality of specific metal materials, which brings great convenience for production, use and management.
8 Varieties The types of metallic materials refer to products with different uses, shapes, production processes, heat treatment conditions, particle sizes, etc.
9 Models The model of metal materials refers to the code used to represent products with different shapes and types of profiles and hard alloys by using Pinyin (or Latin) letters and one or several numbers. The number indicates the nominal size of the main part
10 Specifications The specification refers to different sizes of the same type or the same type of metal material. Different sizes generally have different allowable deviations. In the product standard, the specifications of the products are usually ordered from the smallest to the largest.
11 The surface state is mainly divided into two kinds: bright and not bright. Common in wire and steel strip standards, the main difference is whether to adopt bright annealing or general annealing. It also treats polishing, polishing, pickling, plating, etc. as surface conditions.
12 Edge state Edge state refers to whether or not the strip is trimmed. The trimmer is a trimmed strip, and the trimmer is not trimmed.
13 Delivery status The delivery status refers to the final plastic deformation or final heat treatment of the product delivery. Hot-rolled (forged) and cold-rolled states are delivered without heat treatment. After normalizing, annealing, high-temperature tempering, quenching and tempering, and solid solution treatment, they are collectively referred to as the heat treatment state delivery, or according to the heat treatment category, they are called normalizing, annealing, high-temperature tempering, and tempered state delivery.
14 The degree of softness and hardness of materials refers to the degree of hardness and hardness of the steel obtained by adopting different degrees of heat treatment or work hardening. In some steel strip standards, it is divided into special soft steel strip, soft steel strip, semi-soft steel strip, low-hard steel strip and hard steel strip.
15 Longitudinal and Lateral The longitudinal and transverse directions referred to in the steel standards refer to the relative relationship between rolling (forging) and drawing direction. The direction parallel to the machining direction is called vertical; the one perpendicular to the machining direction is called transverse. The sample taken along the machine direction is called the longitudinal sample; the sample taken perpendicular to the machine direction is called the transverse sample. The fracture on the longitudinal specimen is perpendicular to the rolling direction, so it is called transverse fracture; the fracture on the transverse specimen is parallel to the processing direction, so it is called longitudinal fracture.
16 Theoretical and actual quality This is two different ways of calculating the quality of delivery. Those who deliver according to theoretical quality are the quality of delivery calculated according to the nominal size and density of the material. The actual quality of delivery is based on the quality of the material (weighed)
17 Nominal size and actual size Nominal size refers to the nominal size specified in the standard and is the ideal size desired in the production process. However, in actual production, the actual size of steel is often larger or smaller than the nominal size. The actual size obtained is called the actual size.
18 Deviations and Tolerances Because it is difficult to achieve nominal dimensions in actual production, the standard states that there is a permissible difference between the actual size and the nominal size, called the deviation. The negative value is called negative deviation, and the positive value is positive deviation. The sum of the allowable positive and negative deviations specified in the standard is called the tolerance. The deviation is directional, ie, expressed as "positive" or "negative," and the tolerance has no directionality.
19 Delivery Length There are four provisions in the current standard for the length of delivery of steel products:
(1) Normal length - also known as indefinite length, where the length of the steel is within the standard range and has no fixed length, it is called the normal length. However, for the convenience of packaging, transportation, and metering, it is advisable for companies to cut into several different lengths depending on the situation in order to avoid chaos.
(2) Length of fixed length - The fixed length cut according to the ordering requirements (the length of the steel plate refers to the width and length) is called the length of the fixed length, for example, the length of the fixed length is 5m, then the length of a batch of delivered steel is 5m. But in practice it is impossible to be 5m long, so it is also stipulated that the allowable positive deviation value
(3) Length of doubler - The single length of the order is cut into an integral multiple of the length of the order. It is called the length of the doubler. For example, the length of the singler is 950mm, and the length of the doubler is 1900mm. The triple ruler is 950×3=2850mm, etc.
(4) Where the length is less than the lower limit of the normal length in the standard, but not less than the minimum allowable length, it is called the short length
20 Smelting method It refers to the type of steelmaking furnace smelting, for example, smelting with open hearth, electric arc furnace, electroslag furnace, vacuum induction furnace and mixed steelmaking. The meaning of the term “smelting method†in the standard does not include the concepts of deoxidation methods (eg, fully deoxygenated killed steel, semi- deoxidized semi-killed steel and boiling steel) and casting methods (such as bets, bets, and continuous castings).
21 Chemical composition (product composition) refers to the chemical composition of steel products, including principal components and impurity elements, the content of which is expressed in weight percent
22 Melting components Melting components of steel means that the steel is completed in the melting (such as deoxidation in the tank) and the chemical composition in the middle of the casting
23 Finished product The final product composition of steel, also called verification analysis component, refers to the chemical composition obtained from the finished steel product that has been drilled or shaved by the prescribed method (see GB/T222 for details) and analyzed according to the specified standard method. . The finished product composition of steel is mainly used by the use department or the inspection department for acceptance of steel products. Manufacturers generally do not complete product analysis, but should ensure that the finished product components meet the standards. Some major products or sometimes due to some reasons (such as process changes, quality instability, smelting components close to the upper and lower limits, smelting analysis has not been taken, etc.), the production plant also do the final product analysis
24 High-quality steel and high-grade steel (with A-letter) Also known as quality steel and high-grade steel, the difference is that high-quality steel is superior to high-quality steel in some or all of the following aspects:
1Reduce carbon content range; 2Reduce harmful impurities (mainly sulfur, phosphorus) content; 3Ensure higher purity (refer to less inclusion content); 4Ensure higher mechanical properties and process performance
4. Steel delivery status Steel delivery status No. Name Description
1 Hot-rolled steels are not subjected to special heat treatment after hot rolling or forging. Direct delivery after cooling is called hot rolling or hot forging. The termination temperature of hot rolling (forging) is generally 800 to 900°C. Normally, it cools naturally in the air, so the hot-rolled (forged) state corresponds to normalizing. The difference is that because the hot rolling (forging) termination temperature is high or low, unlike the normalized heating temperature control is strict, so the fluctuation of the organization and performance of the steel is greater than normalizing. At present, many iron and steel enterprises use controlled rolling. Due to the strict control of the final rolling temperature and forced cooling measures after the final rolling, the grains of the steel are refined, and the delivered steel has higher comprehensive mechanical properties. The reason why the non-twist-controlled hot-rolled wire rod has better performance than ordinary hot-rolled wire rod is this principle. Steels delivered in the hot-rolled (forged) state have a certain degree of corrosion resistance due to the surface covered with a layer of scale of iron oxide. The requirements are not as stringent as the steels delivered in the cold-rolled state. Large- and medium-sized steel and medium-thick steel plates can be stored in the open yard or after the lid is placed.
2 Cold drawing (rolling)
State Cold-drawn, cold-rolled and cold-formed steels are delivered directly without any heat treatment and are called cold-drawn or cold-rolled. Compared with the hot-rolled (forged) state, the cold-rolled (rolled) steel has high dimensional accuracy, good surface quality, low surface roughness, and high mechanical properties due to the delivery of cold drawn (rolled) steel. The surface is not covered with oxide scale, and there is a lot of internal stress, and it is vulnerable to corrosion or rust. Therefore, the cold drawn (rolled) steel has strict requirements for packaging, storage, and transportation, and generally needs to be stored in the warehouse. And pay attention to the temperature and humidity control in the warehouse
3 Normal state Steel products undergo normal heat treatment before they leave the factory. This delivery state is called normalizing. Since the normalizing heating temperature (Ac3+30 to 50°C for hypoeutectoid steel and Accm+30 to 50°C for hypereutectoid steel) is more strictly controlled than the hot rolling termination temperature, the structure and performance of the steel material are uniform. Compared with the steel in the annealed state, due to the faster normalizing cooling rate, the amount of pearlite in the steel structure increases, and the pearlite layer and the grain of the steel become finer, resulting in a higher comprehensive mechanical performance, and is beneficial to improvement The Weigang structure of low carbon steel and the cementite network of hypereutectoid steel can be used to prepare for further heat treatment of finished products. Carbon steel and joint steel materials are often delivered under normalized conditions. Some low-alloy high-strength steels such as 14MnMoVBRE, 14CrMnMoVB steel also require normalized delivery in order to obtain the bainite structure.
4 Annealed state Steel is annealed and heat treated before being shipped from the factory. This type of delivery is called an annealed condition. The purpose of annealing is mainly to eliminate and improve the organizational defects and internal stresses left over from the previous process, and to prepare for the subsequent processes in terms of organization and performance. Alloy structural steel, hardenability structural steel, cold-headed steel, bearings Steel, tool steel, turbine blade steel, wire rope stainless steel heat-resistant steel commonly used annealing delivery
5 high temperature tempering steel before leaving the factory by high temperature tempering heat treatment, this delivery state is called high temperature tempering state. The tempering temperature of high temperature tempering is high, which is conducive to the complete elimination of the internal stress and improves the plasticity and toughness. The carbon structure, alloy steel, and hardenability structural steel steel can be delivered at high temperature and tempered state. Some martensitic high-strength stainless steels, high-speed tool steels and high-strength alloy steels, due to their high hardenability and the strengthening effect of alloying elements, often undergo a high-temperature tempering after quenching (or tempering) to make steels. The carbides are properly aggregated to obtain a coarser tempered sorbite structure with carbide grains (similar to the spheroidized annealed structure). Therefore, the steel in this delivery state has excellent machinability.
6 Solution treatment state The steel is solution-treated before being shipped from the factory. This delivery state is called solid solution treatment. This state is mainly applied to the processing of austenitic stainless steel before leaving the factory. Through solution treatment, single-phase austenite structure is obtained to improve the toughness and plasticity of steel, create conditions for further cold processing (cold or cold drawing), and also prepare for further precipitation hardening.
Steel Standard Terms
1 Standards Standards are uniform rules for repetitive things and concepts. It is based on the comprehensive results of science, technology and practical experience. It is approved by the competent authorities after consultation among relevant parties and is issued in a specific form as a criterion and basis for mutual compliance. At present, there are national standards (GB, GB/T), industry standards (YB), local standards, and corporate standards for the implementation of steel products in China.